/*
* INSANE - Interactive Structural Analysis Environment
*
* Copyright (C) 2003-2005
* Universidade Federal de Minas Gerais
* Escola de Engenharia
* Departamento de Engenharia de Estruturas
* 
* Author's email :    insane@dees.ufmg.br
* Author's website :  http://www.dees.ufmg.br/insane
* 
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or any later version.
* 
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
* 
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*/
package br.ufmg.dees.insane.solution;

import br.ufmg.dees.insane.util.IMatrix;
import br.ufmg.dees.insane.util.IVector;

/** 
 * A class defining a
 *
 * @author Fuina, Jamile & Pitangueira, Roque
 * @since July 2005
 */
/**
 * @author jamile
 *
 */
public abstract class ArcLengthControl implements IteractiveStrategy {
    
	protected Step step;
    private double loadFactor;
    protected double arcLength;
    protected double lambda;
    protected IVector incXinicial;
    protected IVector incX;
    int q =1;
    
    public ArcLengthControl() {
    } 
    
    /**
     * @param loadFactor the displacement adopted to the Displacement Control Strategy
     */
    public ArcLengthControl(double loadFactor) {
		this.loadFactor = loadFactor;
	}  
    
    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#getPredictor()
     */
    public double getPredictor(){
        incXinicial = new IVector (this.step.getAssembler().getSizeOfXu());
        incX = new IVector (this.step.getAssembler().getSizeOfXu());
        IVector xp = this.step.getXP();
    	if (q == 1){
    		this.arcLength = this.loadFactor * Math.sqrt(xp.dot(xp));
    	}
    	
    	lambda = this.arcLength / Math.sqrt(xp.dot(xp));  
    	lambda = this.getPivot(this.step.getAssembler().getIncrementalCuu()) *  lambda;
    	incXinicial.scale(lambda, xp);
    	incX.add(incX, incXinicial);
    	q++;
    	return lambda;			
    }	

    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#getCorrector()
     */
    public abstract double getCorrector();		
    	
    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#getLoadFactor()
     */
    public double getLoadFactor() {
        return loadFactor;
    }
    	
    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#setLoadFactor(double)
     */
    public void setLoadFactor(double lf){
    	this.loadFactor = lf;
    }
    
    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#getLambda()
     */
    public double getLambda() {
        return lambda;
    }
           
    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#setStep(Step)
     */
    public void setStep(Step sp){
    	this.step = sp;
    }
    
    /* (non-Javadoc)
     * @see br.ufmg.dees.insane.solution.IteractiveStrategy#getStep()
     */
    public Step getStep(){
    	return step;
    }
    
    private double getPivot(IMatrix c){
    	double min = c.getElement(0,0);
    	for (int i=1; i< this.step.getAssembler().getSizeOfXu(); i++) {
			if (c.getElement(i,i) < min)
				min = c.getElement(i,i);
		}
    	if (min < 0.0) min = -1.0;
    	else min = 1.0;
    	
    	return min;
   }

}
